I don't know. In that emergency threat I mentioned before, I was told that there could be a link between vitamin deficiencies and cataracts, or it could be a genetic defect. I'm actually leaning towards an issue with the hatchery because the other black Maran I got at the same time has also developed cataracts, And all the other chicks I got from the same hatchery are perfectly normal. So if anyone wants the black Maran for free who's almost blind, send me a PM.How did she become blind?